The present invention relates to a thermal spray powder and a thermal spray coating.
Hard chrome plating was often applied to surfaces of rolls such as corrugated rolls used in paper or film manufacturing lines. However, in recent years, tungsten carbide (WC)-based cermet thermal spray coatings have been used instead (see, for example, Japanese Laid-Open Patent Publication Nos. 8-60596 and 2006-29452).
A thermal spray coating generally has a high surface roughness. Thus, for use of a thermal spray coating in rolls, its surface roughness has to be reduced by polishing. In order to obtain a thermal spray coating with a low surface roughness for reducing the effort of polishing, it is known to be effective to use a thermal spray powder with a small particle size (see, for example, Japanese Laid-Open Patent Publication No. 2003-129212). However, a thermal spray coating formed from a thermal spray powder with a small particle size has an extremely lower wear resistance than that formed from a thermal spray powder with an ordinary particle size, and thus is not suitable for use in rolls.